Sometimes, the math intensity in economics does not correlate to the school’s admission selectivity.
For example, UC Santa Cruz requires some multivariable calculus for its intermediate microeconomics courses, while some more selective schools like Florida State and Penn State do not even list calculus as a prerequisite (except for the honors course at Penn State which lists single variable calculus – the honors course has far smaller enrollment than the regular course). Georgia Tech’s intermediate microeconomics course does not list any math prerequisites in the catalog, though the syllabus indicates some basic calculus is used.
With respect to Penn, it also offers a liberal arts economics major (in its arts and sciences division) which is math-intensive.